Looking at the dataset Animals2, available in R, which contains average brain and body weights for 62 species of land mammals and three dinosaurs, we wanted to answer the question of how well the body weight predicts the brain weight of a land animal.
At the same time, we were interested to know how well this prediction works if we split our group into subgroups, for example if we have a group only with rodents, or one only with primates, or one without the dinosaurs. Also, are there outliers in the main group and in the subgroups? If yes, which animals are those outliers?
Animal data is coming from:
Weisberg, S. (1985) Applied Linear Regression. 2nd edition. Wiley, pp. 144–5.; P. J. Rousseeuw and A. M. Leroy (1987) Robust Regression and Outlier Detection. Wiley, p. 57.